Macromolecular materials having self-restoring and shape memory properties have been actively researched and developed in recent years. In particular, in view of the recent incessant occurrence of accidents caused by damage and deterioration of materials, enhancing the reliability of materials is considered to be highly useful. One approach for enhancing the reliability of materials is to increase the durability of the materials themselves. If a material has a self-restoring function in addition to durability, reliability with regard to safety is increased and cost advantages are also attained.
When such a self-restoring macromolecular material is used as a member of or a surface-coating agent for cellular phones, displays, automobiles, etc., even if the material is damaged, the damage can be spontaneously repaired. Therefore, the self-restoring macromolecular material is considered to be highly useful in terms of enhancing product durability and also maintaining design for a long period of time. However, in order to enhance mechanical strength, etc., general macromolecular materials are formed into a three-dimensional network structure by covalent crosslinking between chain macromolecules. When stress is applied to such a macromolecular material, the stress tends to concentrate on short portions of the three-dimensional network, thus leading to material damage. Once the bonds in crosslink points of the three-dimensional network are broken, bonding back to the original state (rebonding) is impossible. Therefore, self-restoration is usually difficult. Accordingly, in order to impart a self-restoring function to a macromolecular material, for example, Patent Literature 1 (PTL 1) proposes a crystalline macromolecular crosslinked product composed of a macromolecular crosslinked structure and many dangling chains bonded to the macromolecular crosslinked structure (i.e., partial chains with one end being linked to the crosslinked structure and the other end being not linked to the crosslinked structure). This macromolecular crosslinked product exerts a self-restoring function through entanglement interaction of the dangling chains, which become active at the crystalline melting point or a higher temperature.